feat: add swift implementation to lcof2 problem: No.079 (#3458)

Author: klever34

lcof2/剑指 Offer II 079. 所有子集/README.md

@@ -188,6 +188,27 @@ impl Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func subsets(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        dfs(0, nums, [], &res)
+        return res
+    }
+    
+    private func dfs(_ i: Int, _ nums: [Int], _ current: [Int], _ res: inout [[Int]]) {
+        res.append(current)
+        for j in i..<nums.count {
+            var newCurrent = current
+            newCurrent.append(nums[j])
+            dfs(j + 1, nums, newCurrent, &res)
+        }
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 079. 所有子集/Solution.swift

@@ -0,0 +1,16 @@
+class Solution {
+    func subsets(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        dfs(0, nums, [], &res)
+        return res
+    }
+    
+    private func dfs(_ i: Int, _ nums: [Int], _ current: [Int], _ res: inout [[Int]]) {
+        res.append(current)
+        for j in i..<nums.count {
+            var newCurrent = current
+            newCurrent.append(nums[j])
+            dfs(j + 1, nums, newCurrent, &res)
+        }
+    }
+}